ANIMAL PARASITES 109 



considerable numbers by scraping the mucosa with the dull 

 edge of a scalpel into a Petri dish with physiological salt solution. 



To recover the adult worms in large numbers the following 

 method has proved very satisfactory: 



Starve a rat for 2 days and then feed it a piece of heavily 

 trichinosed tissue about the size of the end of the thumb. Keep 

 the animal unfed for 2 more days to eliminate intestinal debris, 

 kill, and remove the intestine to a container filled with warm 

 water. 



Take short unslit pieces of the intestine and, holding with 

 forceps over a vial filled with water, strip toward the free end 

 with another pair. Apply sufficient pressure to remove all of 

 the intestinal contents without tearing the intestine itself. 



Emulsify the extruded material by vigorously shaking to dis- 

 entangle the worms from what little debris is present. Screen 

 this out by emptying the vial on a 40-mesh screen placed over a 

 stender dish filled almost to the rim with water. The screen 

 should sag well below the water surface. The worms soon work 

 their way through into the water and drop to the bottom where 

 they may be recovered. 



For permanent mounts kill specimens in hot 70 per cent alcohol. 

 Change to fresh 70 per cent alcohol for preservation. Dehy- 

 drate gradually through the alcohols, clear in xylol, and mount 

 in thin damar or balsam. 



PERMANENT MOUNTS OF HELMINTH EGGS 



Fecal material containing eggs or cysts of parasitic forms 

 may be preserved in 10 per cent formalin solution, with or with- 

 out previous sedimentation. The fluid should be changed 

 occasionally as the offensive odor is greatly reduced by this 

 procedure. 



Langeron adds 10 per cent of glycerine as the eggs are thus 

 rendered more transparent. They can be mounted in this fluid 

 and sealed with Noyer's cement, but we have found that such 

 preparations are not likely to be satisfactory for more than two 

 or three years. 



The best method of permanent mounting of helminth eggs in 

 feces is that of Looss. A well-sedimented and sieved specimen 

 with just enough water to make a thin paste is gradually added, 

 with constant stirring, to hot, almost boiling 70 per cent alcohol 

 plus 5 per cent glycerine, and allowed to cool. When cold the 



